It is well known in the art of drilling oil and gas wells, to place stabilizers in the string of drill pipe, above the drill bit. These stabilization tools employ two basic methods of maintaining the orientation of the drill bit about its axis and ideally, also the drill string axis of rotation. Such tools minimize drift of the borehole from the vertical or any other preferred azimuthal angle. The first method is tool rigidity itself and the second method is to contact the well bore wall. Inasmuch as continual circulation of drilling fluid down through the inner bore of the drill string and returning up through the annular area between the drill string and the bore hole wall must be maintained, the second method of stabilization is most usually obtained through the use of “ribs,” “ridges” or “blades” which protrude out from the main body of the tool in contact with the bore hole wall. The interstitial area between these blades provides the annular area or volume necessary for return of circulating fluid used in rotary drilling operations.
The bodies of the conventional stabilizer, as well as the ribs or blades, are typically manufactured from mild steel. Because the tool's rib surfaces are in constant contact with the borehole wall to provide maximum stabilization and prevent azimuthal deviation, these ribs in the prior art are provided with protection against the erosion and abrasion effected by hard abrasive geologic formations. If not protected by hard metal stripping or insertion of ultra-hard material into the mild carbon steel, the contacting surface will abrade and the tool will progressively lose its effectiveness. Use of such inserts in such a tool is disclosed, for example, in U.S. Pat. No. 4,304,311 and U.S. Pat. No. 4,156,374.
The present invention is a marked improvement over the use of ultra-hard inserts, buttons or pads used with the mild steel bodies and ribs known in the stabilizer arts.
Since the 1950's, powdered metal infiltration casting has been used to manufacture drill bits. In the 1950's through the 1970's, natural diamond bits were manufactured with this process. It is common practice today to manufacture PDC bits with this same process, inherited from the natural diamond bits.
The present invention uses powdered metal infiltration casting to manufacture a drill string stabilizer whose primary function is to stabilize the drill string centrally within a previously drilled hole. In manufacture, the stabilizer does resemble a reaming tool in that it requires both an upper and lower oilfield connection. But the primary purpose of this tool is stabilization, and the reason for this method of manufacture is to produce a more wear resistant body by using tungsten carbide as the primary metallic element in the stabilizer blades and body.
By manufacturing the contact surfaces of infiltrated tungsten carbide, the predominant element in the contact zones is tungsten carbide, which is more resistant to wear, and thus maintains the outer diameter of the stabilizer for far longer than steel. This results in a stabilizer which is more robust than the current standard, steel.
Additionally, the technology used in drill bits to retain outside diameter can be utilized in a stabilizer. This includes the capacity to place PDC wear elements in the contact zones, as well as thermally stable PDC elements, tungsten carbide tiles, natural diamonds and similar ultra-hard materials. New technology within the drill bit industry allows for infiltrated tungsten carbide (referred to hereafter as matrix) to be repaired by welding and brazing with specialized metallic compounds.